A ship mounted video is a cheap and widely used method to determine ice thickness. Apart from methodical caveats it must be considered, however, whether the ship's tendency to seek easily navigable routes within the ice introduces a bias to the thickness determination. In this paper thickness data from a ship mounted video is compared with direct measurements by electromagnetic sounding. The data was collected from the Kara/Laptev Sea sector of the Central Arctic Basin during a 2 month cruise in 1996. There is no systematic difference between the two thickness data sets.